Idiopathic ulcerative dermatitis

From Felipedia

Ulcerative idiopathic dermatitis is a rare, clinically distinctive skin disease of cats.

Due to its localization it should be considered in the differential diagnosis of the self harming (scratching) secondary ulcerative dermatitis that affect the dorsal area of the neck. The cause and pathogenesis of this problem is unknown. It has been suggested that neither the trauma, injections, foreign bodies or infectious agents would have anything to do in the development of this process, afterwards and due to the location of the injury, it has been suggested as possible cause a hypersensitivity reaction towards injected drugs or applied topically (treatments or vaccines). Nevertheless, there have been cases described in which cats apparently had not received injections in the area. Another hypothesis about the pathogenesis is an over-stimulation of the local sensorial nerval fibres due to several causes with a behavioural component associated or vascular alterations in the dermal vessels with the consequent necrosis post-ischemic.

Clinically, the characteristic presentation of idiopathic ulcerative dermatitis is an area of focal alopecia with an ulcer localised in the thoracic middle line in between the scapula and the dorsal part of the neck. It is a well limited ulcer (2-5 cm in diameter) with high borders in the more chronic lesions and usually presents with a well attached brownish scab. Initially, pruritus or pain may be absent, however, pruritus of the area usually manifests at some time later during the disease process. In some cases it is possible to observe an enlargement of the local linphonodes. It has not been described a predisposition by age, breed or gender.

The condition it is clinically distinctive which makes for not a lot of differential diagnosis. It is important to be able to differentiate if the injury is secondary to an external factor like a chemical or thermal burn or to a self injury. In the feline species the continuous grooming, which normally affects to the head and/or neck, it is associated with self harming injuries (abrasions, ulcers, haemorrhagic scabs and partial alopecia). In case of clinical history with excessive grooming, the following conditions need to be considered in the differential diagnosis if it is not possible to probe the spontaneous character of the injury:

• Allergic dermatitis (environmental allergens, fleas, other external arthropods, food)
• Parasitic dermatitis (demodicosis, others)
• Dermatophytosis
• Reaction (non neoplastic) to injected drugs (panniculitis, vasculitis)
• Neoplasia, specially a type of squamous cell carcinoma

The diagnosis of the feline idiopathic ulcerative dermatitis is confirmed clinically with a dermopathological examination. However, in case of presenting a case with scratching symptoms, it is recommended to initiate the diagnostic protocol prior to the skin biopsy.

1. Microscopic examination of superficial or deep scraping, the flares or aural secretion if presents.

2. Wood light examination and trichoscopic examination. In case of negative results, it also advisable to rule out a dermatophitosis by a mycological culture.

3. Cytological examination by impression. If by cytological examination shows signs of bacterial infection, we should start a systemic antibiotic treatment.

4. If no parasitic agents are found, it is recommended anyway to start a preventive antiparasitic treatment against fleas and mites while waiting for the mycological treatment. It is recommended as well to start a broad spectrum antibiotic therapy.

5. If after ruling out a dermatophytosis, introducing an antiparasitic treatment, and treating a possible bacterial infection the problem still continues, it is convenient to perform a skin biopsy to confirm/rule out the presence of an allergic dermatitis, reaction to injected drugs, neoplasia or an idiopathic ulcerative dermatitis. It is recommended to perform an scitional biopsy of the margins of the ulcer. However as in the case of idiopathic ulcerative dermatitis, the complete excision can be curative, if the suspicious is strong enough, it should be considered the complete and deep excision, including the subcutaneous tissue.

Histologically the idiopathic ulcerative dermatitis is characterised by a necrotic and ulcerative dermatitis with little perivascular to interstitial neutrophilic inflammatory infiltrate. In the chronic lesions there is a lineal fibrosis in the superficial dermis, next to an intact epidermis. In some cases it has been described thrombus in the dermal vessels, suggesting as a possible pathogenesis a post-ischemic necrosis and a reparative fibrosis. Sometimes it is a process of difficult treatment. Some wounds are to big for a successful complete excision as treatment, and unfortunately there is a relapse after surgery. Traditionally a systemic treatment with glucosteroids has been used (metilprednisolone acetate, oral prednisolone/metilprednisolone). It has been reported, anecdotally, the use of glucocorticoids creams topically and keeping the lesion protected from scratching or licking with a soft bandage or a baby t-shirt.

References

1.Scott DW: An unusual ulcerative dermatitis associated with linear subepidermal fibrosis in eight cats. Feline Practice 1990; 18(3):8-11.

2.Scott DW, Miller WH, Griffin CE (eds): Feline ulcerative dermatitis with linear subepidermal fibrosis. En: Muller & Kirk’s Small Animal Dermatology, Philadelphia, WB Saunders, 2001; 1167-1168..

3.Gross TL, Ihrke PJ, Walder EJ, Affolter VK (eds): Feline idiopathic ulcerative dermatosis. En: Skin diseases of the dog and cat. Clinical and histopathologic diagnosis, 2nd edition, Blackwell Science Ltd, 2005; 130-132.

4.Spaterna A, Mechelli L, Rueca F, Cerquetella M, Brachelente C, Antognoni MT, Tesei B. Feline idiopathic ulcerative dermatosis: Three cases. Vet Res Comm 2003; 27 Suppl.1:795-798.